Surface traversing apparatus with stepped running surface

ABSTRACT

The surface traversing apparatus includes a main body having a shovel that curves upwardly at the front thereof. A rider is releasably secured to the top surface of the surface traversing apparatus by a binding that holds the rider&#39;s boots. The surface traversing apparatus further includes a diffuser, which defines a stepped running surface, positioned on the bottom rear portion of the apparatus. The diffuser operates to reduce both parasitic drag and form drag while providing increased directional stability when the surface traversing apparatus runs flat against the snow.

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication Serial Nos. 60/298,844, filed Jun. 15, 2001, and 60/351,188,filed Jan. 23, 2002, which are hereby incorporated by reference.

FIELD OF THE INVENTION

[0002] The present invention relates generally to surface traversingapparatuses for carrying a rider on snow, and more particularly to skisand snowboards.

BACKGROUND OF THE INVENTION

[0003] For purposes herein, the term ski shall refer to both downhillskis and snowboards. For racing as well as general ski use, it isdesirable to have the ski slide as freely as possible over the snow. Forpractical purposes, a free sliding ski will travel further over thesnow, extending the glide for the user and minimize any skating andpushing with ski poles or other methods required to traverse flatground. A free sliding ski is easier to maneuver, requiring lessphysical effort by the user to initiate turns. And finally, a freesliding ski will gather greater speed for the racing enthusiast, nettinga lower time through the racecourse.

[0004] Many factors contribute to the sliding performance of a ski. Thegeneral physical dimensions and shape of the ski are important, as wellas the component parts. In the construction of a ski, a great deal ofattention is focused in such areas as stiffness in both flex andtorsion, running surface length and base material, side cut, anddampening. The ski engineer addresses these construction criteriathrough the utilization of various materials and methods, therebytailoring the ski's performance envelope to meet the categorized abilitylevels of the skiing public. The dynamic motion of a ski over the snowis the sum of its component parts acting in concert, resulting in theskis ultimate glide and control characteristics.

[0005] Generally described, the performance of skis as they slide overthe snow in flat or near flat angular relation to the snow surface isaffected by several factors that contribute to the skis glide andcontrol capabilities. First, parasitic drag is one opposing force withrespect to glide. Parasitic drag is a term used to define the number ofmolecules of a particular medium (in this case snow) in direct physicalcontact with the ski. The length of the ski and side cut physicallydefine the wetted surface of the ski in contact with the snow. The morewetted surface in contact with the snow, the greater the parasitic drag.Various base materials, waxes and base grinds have been designed to beapplied to the ski base to reduce the interactional effects in theboundary layer between the wetted surface of the ski and the snow.However, drag reduction as a result of base preparation, is stilldependent upon the amount of wetted area the ski applies to the snowsurface.

[0006] A second contributing factor to glide performance is form drag.This type of drag is the dependent upon the shape of the ski. Thephysical footprint the ski applies into the snow defines it drag form.Fluid dynamics teaches that streamlining an object reduces the dragimparted upon the object (ski) as it proceeds (in this case) over, orthrough a medium.

[0007] The ski is limited with regard to the amount of designstreamlining that can be added to the basic shape by other performancerequirements, primarily turning characteristics. A ski requires a sidecut in order to achieve a turn. The amount and specific shape of thecurved side cut acting jointly with the designed flex, determine theskis turning capabilities and qualities. In terms of design priority, aski is designed first and foremost to fit turning criteria for theperformance application envisioned by the engineer. As the hourglassperimeter shape or side cut of a ski is essentially locked in bypredetermined turning requirements, the opportunity for form dragreduction is greatly reduced.

[0008] Lastly, a third factor related to maximizing glide is trackingstability. Directional control of a ski is a function of the angledeveloped between the ski and the surface of the snow. That is to say,as the ski is angled to one side, the edge engages the snow and appliesa force that changes the skier's direction or track. Edging and turningis the action used by the skier to control speed. Conversely, as theangle is decreased, the force applied by the edge is reduced andultimately becomes zero, at which point the ski is flat against the snowsurface. With the ski running flat, the edges are disengaged from thesnow and the ski becomes directionally unstable. The ski in thiscondition, of its own accord, cannot track straight. As the ski glidesforward and impacts various bumps and undulations in the naturalterrain, angular forces are imparted to ski. These forces cause the skito change the direction of travel. The skier in turn must continuallymake fine edging adjustments to control direction and maintain astraight course. These fine edging adjustments contribute to the dragcoefficient of the ski when running flat.

SUMMARY OF THE INVENTION

[0009] In accordance with aspects of the present invention, a ski orsnowboard is presented that addresses the performance of the ski as itslides over the snow in flat or near flat angular relation to the snowsurface. As described above, the reduction of wetted area is paramountin minimizing the effects of parasitic drag. The invention reduces thewetted area of the ski in flat relation to the snow surface.Additionally, the invention effectively streamlines the base of the skiwithout modifying the two dimensional outline shape, thereby reducingform drag. Further, the invention enhances straight-line stability ofthe ski to assist the skier in minimizing directional inputs, alsoreducing drag.

[0010] In accordance with one embodiment of the present invention, abase of a runner for gliding over snow is provided. The base includes afront portion including a flat running surface generally defining afirst surface plane, and a rear portion. The rear portion includes acentral running surface and a first inner edge located along at least aportion of the perimeter of the central running surface. The basefurther includes a first outer portion disposed adjacent the centralrunning surface. The first outer portion includes a first outer runningsurface and a first outer edge located along at least a portion of theperimeter of the first outer running surface. At least a portion of thefirst inner edge is at a different elevation than the first surfaceplane.

[0011] In accordance with another embodiment of the present invention, asnow traversing apparatus is provided that includes an elongate bodyhaving a front end, a rear end, a top surface, and a base that extendsalong the approximate length of the body. The base includes a frontportion extending between approximately the longitudinal midpoint of theelongate body and the front end. The front portion defines a frontrunning surface that is planar across the entire front portion in thelateral direction as the front running surface extends to the end of thebody. The base also includes a rear portion extending between the end ofthe front portion disposed at approximately the longitudinal midpoint ofthe elongate body and the rear end of the elongate body. The rearportion includes a central running surface generally defining a centralsurface plane, two outer running surfaces, a portion of the centralrunning surface being at a different elevation than the outer runningsurfaces; and first and second inner edges disposed between the centralrunning surface and the first and second outer running surfaces,respectively. The base further includes first and second outer edgessurrounding a portion of the perimeter of the first and second outerrunning surfaces, respectively.

[0012] In accordance with still another embodiment of the presentinvention, a base of a runner for gliding over snow is provided. Thebase includes a front portion including a flat running surface generallydefining a first surface plane, and a rear portion having a removablyattachable stepped portion. The stepped portion includes a centralrunning surface and first and second inner edges located along at leasta portion of the perimeter of the central running surface. The base alsoincludes a first outer portion disposed adjacent to the stepped portion.The first outer surface includes a first outer running surface and afirst outer edge located along at least a portion of the perimeter ofthe first outer running surface. At least a portion of the first inneredge is at a different elevation than the first surface plane. The basefurther includes a second outer portion disposed adjacent to the steppedportion on the side opposite of the first outer portion. The secondouter portion includes a second outer running surface and a second outeredge located along at least a portion of the perimeter of the secondouter running surface. At least a portion of the second inner edge is ata different elevation than the first surface plane.

[0013] Taken together, the present invention endeavors to reduce bothparasitic drag and form drag of the ski while providing increaseddirectional stability while running flat against the snow.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The foregoing aspects and many of the attendant advantages ofthis invention will become more readily appreciated as the same becomebetter understood by reference to the following detailed description,when taken in conjunction with the accompanying drawings, wherein:

[0015]FIG. 1 illustrates a bottom perspective view of a snow ski inaccordance with aspects of the present invention;

[0016]FIG. 2 illustrates a bottom view of the snow ski shown in FIG. 1;

[0017]FIG. 3 illustrates a partial rear side elevation view of the snowski shown in FIG. 1;

[0018] FIGS. 4A-4C illustrates cross-sectional views taken along linesA-A, B-B, and C-C, respectively, in FIG. 3;

[0019]FIG. 5 illustrates a schematic cross-sectional view taken alonglines A-A, section B-B, and section C-C, respectively, in FIG. 3;

[0020]FIG. 6 illustrates a bottom perspective view of a snowboardconstructed in accordance with aspects of the present invention;

[0021]FIG. 7 illustrates a rear partial side elevational view of thesnowboard shown in FIG. 6;

[0022]FIG. 8 illustrates a bottom perspective assembly view of a snowski having a modular design constructed in accordance with aspects ofthe present invention;

[0023]FIG. 9 illustrates a bottom perspective assembly view of asnowboard having a modular design constructed in accordance with aspectsof the present invention;

[0024]FIG. 10 illustrates a cross-sectional view of the ski of FIG. 8without a step liner;

[0025]FIG. 11 illustrates a bottom perspective assembly view of anotherembodiment of the connection between the diffuser and the base of theski/snowboard;

[0026]FIG. 12A illustrates a partial side elevational view of theconnection between the diffuser and the base of the ski/snowboard shownin FIG. 11;

[0027]FIG. 12B illustrates a cross-sectional view of the connectionbetween the diffuser and the base of the ski/snowboard shown in FIG. 11;

[0028]FIG. 13 illustrates a partial side elevational view of anotherembodiment of the connection between the diffuser and the base of theski/snowboard;

[0029]FIG. 14 illustrates a cross-sectional view of yet anotherembodiment of the connection between the diffuser and the base of theski/snowboard;

[0030]FIG. 15 illustrates a bottom view of the ski in accordance withaspects of the present invention showing the wetted area;

[0031]FIG. 16 illustrates a bottom view of the snowboard in accordancewith aspects of the present invention showing the wetted area;

[0032]FIG. 17A illustrates a partial side view of the rear portion ofanother alternative embodiment of the ski in accordance with the presentinvention;

[0033]FIG. 17B illustrates a partial rear side elevation view of thesnow ski shown in FIG. 1; and

[0034]FIG. 18 illustrates an alternative embodiment of a ski showing adiffuser having an inwardly tapering rear portion.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0035] The present invention will now be described with reference to theaccompanying drawings where like numerals correspond to like elements.FIG. 1 illustrates a bottom perspective view of one exemplary embodimentof a snow ski 10 formed in accordance with aspects of the presentinvention. The snow ski 10 includes a main body having a shovel 12 thatcurves upwardly at the front of the snow ski 10. A rider is releasablysecured to the top surface 14 of the snow ski 10 by a binding (notshown) that holds the rider's boots. The snow ski further includes adiffuser 16 positioned on the bottom rear portion of the ski. Thediffuser 16 operates to reduce both parasitic drag and form drag whileproviding increased directional stability when the ski runs flat againstthe snow.

[0036] Referring now to a bottom view of the ski 10 shown in FIG. 2, thebody of ski 10 includes a base 18. The base 18, disposed along thebottom of ski 10, is defined by right and left outer edges 20 and 22. Inthe embodiment shown, the right and left outer edges 20 and 22 arecurved inwardly toward the longitudinal axis of the ski from one end ofthe base to the other end in order to form an hourglass shape thatcurves outwardly towards the front and rear ends of ski. Used herein,the directions of left, right, front, and rear are in the context of theposition of a rider, the part of the ski to the rider's right being the“right side” and so forth. A rider is generally oriented as having aposition generally facing the shovel of the snow ski 10.

[0037] The base 18 includes a substantially flat planar front portion18A having a front running surface and a rear portion 18B having astepped or raised running surface formed via the diffuser 16. The frontportion 18A begins at approximately the waist or longitudinal midpointof the ski 10 and extends to the front end thereof. The rear portion 18Bincludes a central rear running surface 24, and longitudinal side walls.The side walls and the central rear running surface 24 converge at rightand left inner edges 30 and 32. Thus, the central rear running surface24, the inner edges 30 and 32, and the longitudinal side walls, definethe diffuser 16. The rear portion 18B further includes right and leftouter running surfaces 26 and 28, which are disposed adjacent to thesides of the central rear running surface 24. Preferably, the front andrear ends of the right and left inner edges 30 and 32 do not endabruptly, but rather blend to become coplanar with the outer runningsurfaces 26 and 28 (FIG. 3). Thus, in this manner, the central rearrunning surface 24 blends into the outer running surfaces 26 and 28 aswell.

[0038] The diffuser 16 of the base 18 is stepped by forming the centralrear running surface 24 of the diffuser 16 slightly lower in elevationthan the right and left running surfaces 26 and 28 (i.e. the centralrear running surface 24 is spaced a further distance apart from the topsurface of the ski 10 than the right and left running surfaces 26 and28). The right and left running surfaces 26 and 28 are preferably flator straight across laterally, and in this embodiment, are substantiallycoplanar with the front running surface of the front portion 18A. In theembodiment shown, the right and left inner edges 30 and 32 are disposedparallel to the longitudinal axis of the ski 10. Alternatively, as shownin FIG. 18, the right and left inner edges may taper inwardly as theyextend from the beginning of the diffuser to its end to further reducedrag. The central rear running surface 24 is preferably flat anddecreases in elevation when compared to the top surface 14 as thesurface 24 extends rearwardly. Thus, the diffuser 16 is wedge-shaped andincreases in thickness as it extends toward the rear end of the ski 10.

[0039] Alternatively, the central rear running surface 24 of thediffuser 16 may extend rearwardly with an arcuate shape corresponding tothe approximate radius of curvature of the sidecut of right and leftouter edges 20 and 22. In the embodiment shown, the diffuser 16 beginsjust rear of the rider's boot (the oval shown in phantom in FIG. 2) andextends to the rear end of the ski. Alternatively, the diffuser maybegin at approximately the waist or longitudinal mid-point of the ski,or begin at any location between the approximate midpoint of the ski 10and rear end of the ski. In the embodiment shown, the diffuser 16 isintegral with the ski 10. However, as shown in FIGS. 8-14, and describedbelow, the diffuser 16 may be of a modular design that can beselectively attached and detached from the ski body.

[0040] It will be appreciated that the front running surface, thecentral rear running surface 24, and the right and left running surfaces26 and 28 may be formed with a slight curve along their length toprovide camber to the ski.

[0041] FIGS. 4A-4C illustrate cross-sectional views of the ski 10 alongthe lines A-A, B-B, and C-C, in FIG. 3, respectively. As best shown inFIG. 4C, a possible exemplary construction model of ski 10 will now bedescribed. A core 38 is disposed within snow ski 10 and is generallysymmetric about the longitudinal axis of snow ski 10. The core 38 ispreferably constructed of wood and has steps on either sidecorresponding to the stepped base 18. However, a wide variety ofconstruction materials could be used to compose the core, such aspolyurethane or other structural foams. Preferably, the steps of thecore 38 are inside of the right and left inner edges 30 and 32. The core38 is surrounded by a torsion box 40 preferably constructed of acomposite thermoset material such as fiberglass.

[0042] These structural configurations and materials described hereinare exemplary in nature. Other structural configurations or componentsmay also alternatively be used. For example, it is contemplated thatinjection-molding techniques could be used as an alternate boardconstruction methodology. It is also contemplated that materials couldpossibly be utilized which would allow the entire base or even theentire ski or snowboard to be cut from a single piece of material, andthus not require multiple layers of materials. Further, in anotheralternate embodiment of this invention, the edges need not be formed at90-degree angles, but rather could be beveled within a wide range ofangles.

[0043] The running surfaces 24, 26, and 28 are located below the torsionbox 40. The running surfaces 24, 26, and 28 are preferably made of P-Texplastic. P-Tex is the standard material used on bases on standarddownhill skis or snowboards. The central rear running surface 24 isbound on its right and left sides by the right and left inner edges 30and 32, respectively. All of the edges 20, 22, 30, and 32 are preferablystandard metal edges typically used in skis or snowboards. They includeedge ears 42 that project inwardly and are held in place between theP-Tex and fiberglass layers of the running surfaces 24, 26, and 28, andtorsion box 40, respectively. The right and left inner edges 30 and 32are also locked in place by the right and left running surfaces 26 and28 abutting against the right and left inner edges 30 and 32. The rightand left running surfaces 26 and 28 are bounded on their outer sides bythe right and left outer edges 20 and 22, respectively.

[0044] When the word “edge” is used within this application, itdesignates any type of step, (e.g. the right inner edge 30 designatesthe step between the central rear running surface 24 and the right outerrunning surface 26). The word “edge” is not meant to apply only to atraditional metal edge piece. As previously described, it iscontemplated that a snowboard base could be made from a single piece ofmaterial. In this situation the inner and outer edges of the snowboardwould cut into the single piece of material. The “steps” between thecentral running surface and the outer running surfaces in thisembodiment would still be defined as “edges” for purposes of thisapplication.

[0045] To protect the sides of the torsion box 40, right and left sidewalls 44 and 46, disposed above right and left outer edges 20 and 22respectively, shield the sides of snow ski 10. A top layer 48 isdisposed over the entire top surface of the snow ski 10 to protect thetop of torsion box 40, and to support top graphics. The top layer 48 andside walls 44 and 46 are preferably constructed of acrylonitrilebutadiene-styrene (ABS), but may be constructed of other materials.Alternatively, top layer 48 may be integral with the right and left sidewalls 44 and 46 and extend down the sides of snow ski 10.

[0046] Of particular note in FIG. 5 is the angle (α) that represents theedge slope of snow ski 10. Edge slope angle (α) is the angle that theslope of a line between comers of right inner edge 30 and the rightouter edge 20, or between the left inner edge 32 and left outer edge 22,makes with the central rear running surface 24. The edge slope angle isdetermined in this embodiment at the rearward wide point of the ski. Inthe preferred embodiments of the invention, edge slope angle (α) isaround three (3) degrees. However, angles ranging anywhere between 0.1degree and 10 degrees are contemplated. When edge slope angle (α) lieswithin these ranges, snow does not accumulate in the area between theinner and outer edges. Both the height of the step and/or the lateraldistance between the edges may be varied in order to change the edgeslope angle (α).

[0047] While the present invention has been described above andillustrated herein with respect to skis, the diffuser may also beutilized by snowboards to achieve less drag and improved trackingstability. FIGS. 6 and 7 illustrate one suitable embodiment of asnowboard 110 formed in accordance with the present invention. Thesnowboard 110 includes a shovel 112 that curves upwardly at the front ofthe snowboard 110 and a tail 114 that curves upwardly at the rear of thesnowboard 110. A rider is secured to the top of the snowboard 110 bybindings that hold the rider's boots (not shown). The snowboard furtherincludes a diffuser 116 positioned at the bottom of the rear portion ofthe snowboard 10. The diffuser 116 preferably begin at approximately thewaist or longitudinal mid-point of the ski, but can begin at anylocation between the approximate midpoint and rear end of the snowboard110. The diffuser 116 reduces both parasitic drag and form drag whileproviding increased directional stability when the snowboard runs flatagainst the snow.

[0048]FIGS. 8 through 14 illustrate various embodiments of snow skis orsnowboards formed in accordance with aspects of the present invention.The differences between the embodiments illustrated in FIGS. 8-14 anddescribed below lie in the modular design of the diffuser and methods ofselectively attaching the diffuser to the ski body. Although someembodiments are shown with either a snowboard or with a snow ski, itwill be appreciated that the embodiments work equally well with bothskis and snowboards and both should be considered within the scope ofthe present invention.

[0049] Referring now to FIGS. 8 and 9, the diffuser module 216 or 316consists of base material, such as P-Tex, and is attached in thisembodiment by an adhesive. The substructure of the body of the ski 210or snowboard 310 is pre-molded or otherwise formed with the properrecessed diffuser elevation profile 220 or 320 integral to the body ofthe ski 210 or snowboard 310, respectively. In this embodiment, a stepliner may or may not be used. FIG. 10 shows a cross-sectional view ofthe ski 210 where the step liner is not used. It will be appreciatedthat by having a modular design, the diffuser module 216 or 316 can beremoved for repair or modification purposes, and later a new piecereapplied.

[0050]FIG. 11 illustrates another embodiment of a snowboard 410utilizing the modular design of the diffuser 416. The diffuser 416utilizes a detachable backbone or “shoe” structure 422 that defines theelevation profile of the diffuser 416, and provides a semi-rigidplatform to which the diffuser base material 424 attaches. The structure422 can be made from a variety of materials, however a molded durableplastic or phenolic material is preferred. As best shown in FIGS.12A-12B, the diffuser 416 attaches to the body of the snowboard 410 viaa set of tongues 430 that slide through slots 432 in the recessed cavity434 in the snowboard body and are retained with a pin 440 or springloaded ball bearing or other capture mechanism held within an attachmentlug 442.

[0051] Alternative attachment methods, such as various threaded screwdesigns are possible options as well, and is shown in FIG. 13.

[0052]FIG. 14 illustrates yet another embodiment of a ski or snowboard610 utilizing the modular design of the diffuser 616, where the diffuser“shoe” serves as the structure 622 that defines the elevation profile ofthe diffuser 616, and the attachment platform for the base material 624.The diffuser 616 attaches to the ski or snowboard body 613 via a keywaythat is an integral part of the body 613. The diffuser 616 carries thematching shape, keyed to the ski or snowboard body 613. Attachment isaccomplished by engaging the keyed faces 650 of the shoe and the ski orsnowboard 610 at the tail, then sliding the diffuser 616 forward intoplace along the recessed receiver of the ski or snowboard 610. Aremovable pin or screw, or an adhesive may be used to secure thediffuser 616 in place.

[0053]FIG. 17A shows a partial side view of the rear portion of anotheralternate embodiment of a ski or snowboard with a diffuser in accordancewith the present invention. The ski 700 is substantially identical inconstruction, material, and operation as ski 10 described above withrespect to FIGS. 1-4C, except for the following differences which willnow be described in detail. The ski 700 is constructed in a mannerconverse to that previously described with respect to ski 10. Whereas inFIGS. 1 through 14, and for ease of comparison FIG. 17B, the diffuser ofthe ski/snowboard 10 is stepped by forming the central running surfaceslightly lower than the right and left outer running surfaces so thatthe diffuser progressively descends in elevation below the elevation ofthe running base (RBE) in the front portion of the ski and the right andleft outer running surfaces. Conversely, FIG. 17A shows the ski 700having a ski body 713 in which the diffuser 716 is created byprogressively elevating upward from the running base the left and rightouter running surfaces (the central running surface of the diffuserforms the rear portion of the running base of the ski 700). The rightouter running surface forms a progressively elevated outer edge 722. Byconstructing the ski 700 in this manner, the central running surface 724of the diffuser 716 is at substantially the same elevation as therunning base (RBE) of the front portion of the ski. Thus, the runningbase of the front portion, in conjunction with the central runningsurface of the diffuser, forms a continuous and flat running surfacefrom the Forward Contact Point (FCP) to the Rear Contact Point (RCP)with no elevation change in the base.

[0054] Of particular note in this embodiment, a blend radius R isutilized to connect a line formed by the progressively elevated outerrunning surfaces (shown in FIG. 17A as outer edge 722) and the point oftangency with the central running surface. In one embodiment, the blendradius R is approximately equal to the radius of curvature of the sidecut of the right and left outer edges of the ski. In other embodiments,the blend radius may be between 0 and 2 times the radius of curvature ofthe side cuts. It will be appreciated that other radii and shapes arecontemplated to be within the scope of the present invention. While theski 700 is described with respect to FIG. 17A with side cuts having aradius of curvature, it will be appreciated that the present inventionworks equally well with straight skis.

[0055] The ski 700 described above and illustrated in FIG. 17A mayinclude a selectively detachable diffuser as previously described inFIGS. 8-10 and 12-14, and attached as previously described or in variousother attachment methods. Additionally, while the embodiment of FIG. 17Adepicts a ski, it will be appreciated that the new construction methodmay work equally well with snowboards, and thus is within the scope ofthe present invention.

[0056] In accordance with another aspect of the invention, the stiffnessof the diffuser in the various embodiments described above with respectto FIGS. 1-18 can be selected depending on the conditions of the slopeto be traversed and rider preferences. For example, in race conditionswhere the slope is packed with an icy running surface, the rider mayselect a ski with a diffuser having a high degree of stiffness or mayexchange a diffuser with less stiffness for a diffuser with greaterstiffness (for those embodiments having a selectively detachablediffuser), whereas in soft snow conditions, a rider may choose a skihaving diffuser with a lower degree of stiffness. It will be appreciatedthat a set of diffusers can be constructed from known materials so thateach diffuser has a slightly different stiffness, ranging from extremelystiff to extremely flexible.

[0057] The benefits of a ski or snowboard constructed in accordance withthe principles of the present invention will now be described in detailwith reference to FIGS. 15 and 16. FIG. 15 shows the general pressuredistribution of a ski while gliding with the running surface flatagainst the snow utilizing aspects of the present invention. FIG. 16shows the general pressure distribution of a snowboard while glidingwith the running surface flat against the snow utilizing aspects of thepresent invention. The overall wetted area of a conventionalski/snowboard is the entire ski minus the shovel portion, whereas thearea A shown as cross hatched in FIGS. 15 and 16 defines the wettedareas of a ski/snowboard embodied with the present invention. The areasRA and LA on the right and left side of the ski/snowboard, aft of thewaist or longitudinal midpoint outside the area defined by the diffuser,define the areas of reduced direct pressure or an intermittent pressurezone facilitated by the invention. Thus, right and left outer surfacesdefine the areas of reduced direct pressure or an intermittent pressurezone facilitated by the invention. Since the diffuser's elevationincreases in proportion to the widening side cut of the ski aft of thewaist; the diffuser has a smaller wetted area than the actual outline ofthe ski, thereby reducing the amount of parasitic drag.

[0058] Additionally, as a conventional ski/snowboard glides over aparticular area, the snow must pass under the ski/snowboard. Snow lyingwithin the track of the ski/snowboard defined by its narrowest point orwaist is pressurized by the load imparted by the ski. A givenpressurized molecule in this area will pass from the forward wide pointof the ski to the rear wide point, contacting the running base andscribing a hypothetical straight line along the running base definingthe skis trajectory as it passes over that particular molecule of snow.

[0059] However, snow encountering the passing ski outside this centralarea, in the area described as the transition zone, is not continuallypressurized by the passing ski. A given molecule in the transitionalarea will pass under the forward wide point of the ski and will bebriefly pressurized. It will contact the running base and will scribe ahypothetical straight line along the running base defining the skistrajectory. As the ski passes further, the molecule will intersect thenarrowing side cut curve of the perimeter of the ski, and will exit fromunder the outer edge and return to a depressurized state. As the skicontinues to move, due to the curved side cut shape of the ski at thewaist, the width of the ski begins to increase and in effect forms awedge shape. The molecule will re-encounter the edge of the ski at apoint aft of the waist. Due to the curved wedge shape created by theside cut, the molecule collides with the side of the ski and isperpendicularly displaced relative to the skis trajectory a distance Dequal to the maximum width at the rearward wide point. The energy tomove the molecule the required distance is deducted from the inertia ofthe ski and is called form drag.

[0060] The diffuser of the present invention minimizes the effects ofform drag by proportionally reducing or diffusing the load carried bythe outermost, rearward portions of the ski. It accomplishes this with aproportional relative elevation change between the diffuser and theremainder of the rearward base of the ski. The diffuser depressurizesthe drag zones by effectively elevating the drag zone portions of thebase off the snow surface. With the drag zones in a depressurized state,a portion of the molecules that previously would have collided with theside of a conventional ski and be displaced contributing to form drag,instead now pass freely under the side of the ski and are not laterallydisplaced. As the number of molecules perpendicularly displaced relativeto the skis trajectory a distance D have been reduced, energy requiredto move said molecules is reduced and ski inertia is conserved. The skismomentum is better maintained resulting in a faster ski and a ski thatwill glide further.

[0061] The diffuser further provides improved tracking stability to aski or snowboard constructed in accordance with aspects of the presentinvention. A ski gliding flat against the snow surface has minimalstraight-line stability. Directional stability of a conventional ski isderived from the perpendicular opposing forces acting upon the right andleft sides of the ski in the drag zones. When these forces are balanced,the ski proceeds in a straight line. However, as the ski tracks overuneven terrain, the forces become unbalanced. In the unbalanced state,the molecules colliding with the side of the ski in the drag zone aregreater on one side than the other. With the perpendicular forcesunbalanced, the ski pivots about its vertical axis and assumes a newtrack. Since the terrain is rarely flat, the ski does not inherentlytrack straight and the skier must continually initiate small coursecorrections by angling the ski and marginally engaging the edges. Anyengagement of the edges results in a net deduction of inertia from theski and slows the rate of flat glide.

[0062] A ski with greater side cut (smaller turning radius) exhibitsless stability as the angle formed as a function of the skis trajectoryand the side cut at a given molecular point of collision is greater.Therefore, when unbalanced, more perpendicular force is applied to theside of the ski causing it to rotate about its vertical axis at agreater rate. Conversely, a ski with less side cut (larger turningradius) will exhibit better flat straight line stability as theunbalanced perpendicular forces at the collision points will be less,resulting in a slower rotation about the vertical axis.

[0063] As previously described, the diffuser depressurizes the dragzones and reduces the number of molecules perpendicularly displacedrelative to the skis trajectory. Therefore, the total perpendicularforce applied in the drag zone is reduced in the unbalanced state, andthe ski's reaction to pivoting around its vertical axis is reduced inproportion. Straight tracking is therefore enhanced while the ski isflat against the snow.

[0064] Additionally, a second contributing factor to straight-linetracking occurs as a result of the diffuser's shape. The lines formed asa result of the elevation change between the diffuser and the remainingbase of the ski, (i.e. right and left inner edges), are parallel orapproximately parallel to the longitudinal axis and line of trajectoryof the ski. As there is approximately no side cut in the shape of thediffuser, there can be no perpendicular forces acting upon it,therefore, the ski tends to continue tracking straight.

[0065] While the preferred embodiment of the invention has beenillustrated and described, it will be appreciated that various changescan be made therein without departing from the spirit and scope of theinvention. U.S. Pat. Nos. 6,193,244 to Vance; 5,580,078 to Vance; and5,871,224 to Vance are hereby expressly incorporated by reference.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A base of a runner forgliding over snow, the base comprising: a front portion including a flatrunning surface generally defining a first surface plane; a rear portionincluding a central running surface and a first inner edge located alongat least a portion of the perimeter of said central running surface; anda first outer portion disposed adjacent said central running surface,said first outer portion including a first outer running surface and afirst outer edge located along at least a portion of the perimeter ofsaid first outer running surface, wherein at least a portion of saidfirst inner edge is at a different elevation than said first surfaceplane.
 2. The base of claim 1, further comprising a second inner edgeand a second outer portion, said second inner edge being located alongat least a portion of the perimeter of said central running surface onthe opposite side of said central running surface from said first inneredge, said second outer portion being disposed adjacent said secondinner edge, said second outer portion including a second outer runningsurface and a second outer edge located along at least a portion of theperimeter of said second outer running surface, wherein at least aportion of said second inner edge is at a different elevation than saidfirst surface plane.
 3. The base of claim 2, wherein said centralrunning surface is curved longitudinally and is substantially straightacross in a lateral direction along substantially the entire length ofsaid central running surface.
 4. The base of claim 2, wherein saidcentral running surface is substantially planar along substantially theentire length thereof.
 5. The base of claim 2, wherein said first inneredge lies generally parallel to said second inner edge along at least aportion of the length of the base.
 6. The base of claim 2, wherein saidfirst and second outer running surfaces and said first and second inneredges, respectively, are symmetric about the longitudinal axis of thebase.
 7. The base of claim 1, wherein said front surface plane issubstantially coplanar with said central running surface.
 8. The base ofclaim 1, wherein the elevation of said central running surface decreaseswith respect to said first surface plane as said central running surfaceextends in the rearwardly direction.
 9. The base of claim 1, whereinsaid first and second inner edges taper toward the longitudinal axis ofsaid base as said inner edges extend in the rearward direction.
 10. Thebase of claim 1, wherein said central running surface begins at alocation rear of the approximate longitudinally midpoint of the base.11. The base of claim 1, wherein an angle formed between said centralrunning surface and a line running between said first outer edge andsaid first inner edge at the approximate rearward wide point lies in therange of between 0.1 and 10 degrees.
 12. A snow traversing apparatuscomprising: an elongate body having a front end, rear end, a top surfaceand a base that extends along the approximate length of the body, saidbase including: (i) a front portion extending between approximately thelongitudinal midpoint of said elongate body and the front end, saidfront portion defining a front running surface that is planar across theentire front portion in the lateral direction as the front runningsurface extends to said end of said body; (ii) a rear portion extendingbetween the end of said front portion disposed at approximately thelongitudinal midpoint of said elongate body and said rear end of saidelongate body, said rear portion including: (a) a central runningsurface generally defining a central surface plane; two outer runningsurfaces, a portion of said central running (b) surface being at adifferent elevation than said outer running surfaces; and (c) first andsecond inner edges disposed between said central running surface andsaid first and second outer running surfaces, respectively; and (iii)first and second outer edges surrounding a portion of the perimeter ofsaid first and second outer running surfaces, respectively.
 13. Theapparatus of claim 12, wherein said central running surface is curvedlongitudinally and is substantially straight across in a lateraldirection along substantially the entire length of said central runningsurface.
 14. The apparatus of claim 12, wherein a portion of saidcentral running surface is at a lower elevation than said outer runningsurfaces.
 15. The apparatus of claim 12, wherein said front runningsurface is substantially coplanar with said central running surface. 16.The apparatus of claim 12, wherein said central running surface beginsat a location rear of the approximate midpoint of said elongate body.17. A base of a runner for gliding over snow, the base comprising: afront portion including a flat running surface generally defining afirst surface plane; a rear portion having a removably attachablestepped portion, said stepped portion including a central runningsurface and first and second inner edges located along at least aportion of the perimeter of said central running surface; and a firstouter portion disposed adjacent to said stepped portion, said firstouter surface including a first outer running surface and a first outeredge located along at least a portion of the perimeter of said firstouter running surface, wherein at least a portion of said first inneredge is at a different elevation than said first surface plane; and asecond outer portion disposed adjacent to said stepped portion on theside opposite of said first outer portion, said second outer portionincluding a second outer running surface and a second outer edge locatedalong at least a portion of the perimeter of said second outer runningsurface, wherein at least a portion of said second inner edge is at adifferent elevation than said first surface plane.
 18. The base of claim17, wherein a portion of said central running surface is at a lowerelevation than said outer running surfaces.
 19. The base of claim 17,wherein said front surface plane is substantially coplanar with saidcentral running surface.
 20. The base of claim 17, wherein said centralrunning surface begins at a location rear of the approximatelongitudinal midpoint of said base.